Let's not take that route.
The "pollutant" argument is just semantic nonsense. An atmosphere of nitrogen or even O3 (ozone) is just as incapable of supporting life. That's not the point.
The point is that we can have too much (and too little) of a good thing. The GHGs in the atmosphere keep the Earth at a temperature comfortable for human life and all the other life that's evolved here. As has been noted, the biggest contributor to that is water vapor but CO2 and methane and a dozen other lesser compounds have their input into the process. And, of course, CO2 keeps the world's plants alive.
That our atmosphere contains some CO2 is not the result of a human choice. That it contains significantly more than it did prior to the industrial revolution IS. Unfortunately, for the most part of that period, we were ignorant of what the effect of that would be. Now we know better but, still, some folks don't want to act. They are afraid of losing the lifestyles to which they've become accustomed. And many don't like agreeing to act because they see it as a political surrender. The objections of others are religiously-based. And some are simply stupid.
AGW is quite real. It has not ended. It will hurt us all. We need to act. Those are true statements.
